Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h,w = map(int,input().split())
s = [input() for _ in range(h)]

dist = [[-1]*w for _ in range(h)]
dist[0][0]=0
que = [(0,0)]
move = [(0,1),(0,-1),(1,0),(-1,0)]

n_white = 0
for i in range(h):
    n_white += s[i].count(".")

while que!=[]:
    (x , y) = que.pop(0)
    
    for m in move:
        nx = x + m[0]
        ny = y + m[1]
        if (0<=nx<h and 0<=ny<w):
            if dist[nx][ny] != -1: continue
            
            if s[nx][ny] == ".":
                dist[nx][ny] = dist[x][y]+1
                que.append((nx,ny))
distance = dist[-1][-1]
if distance == -1:
    print(-1)
else:
    print(n_white - distance - 1)